U.S. Route 23 in Michigan

Freeway approaching exit 3 in southern Monroe County

US 23 enters Michigan on a freeway northwest of Toledo, Ohio, concurrent with US 223. This freeway runs north through farm fields in rural western Monroe County near Lambertville. About five miles (8.0 km) north of the state line, US 223 leaves the freeway and turns west onto St. Anthony Road; US 23 continues northward on the freeway. South of Dundee, US 23 crosses the River Raisin before coming to an interchange with M-50 next to the Cabela's store west of town. North of town, the freeway passes near an industrial area.[3][4] Farther north, it crosses a line of the Ann Arbor Railroad[7] near Azalia as the trunkline runs to the east of Milan at the Monroe-Washtenaw county line.[3][4] North of Milan, the freeway crosses a line of the Norfolk Southern Railway.[7]

The landscape takes on a more suburban residential character as the freeway approaches the Ann Arbor area. There are separate interchanges for US 12 (Michigan Avenue) and I-94 on the southeast side of the city. Between I-94 and Washtenaw Avenue, US 23 carries the Business Loop I-94 (BL I-94) moniker as well. That secondary designation leaves the freeway and runs west on Washtenaw Avenue into downtown Ann Arbor and the campus of the University of Michigan. At the same interchange, a Business US 23 (Bus. US 23) designation also follows Washtenaw Avenue to the west; east of US 23, M-17 follows Washtenaw Avenue and connects the freeway with Ypsilanti. North of this interchange, US 23 crosses the Huron River near the campus of the local community college and continues north to a junction with the M-14 freeway. The two merge and run westward along the north side of the city before US 23 turns north and M-14 curves south.[3][4]

North of Ann Arbor, the freeway runs through woodlands and near several lakes and features a flex route system allowing traffic to use the inner shoulder during peak times.[8] In the community of Whitmore Lake, US 23 crosses into Livingston County near the city's namesake body of water. East of Brighton, the freeway intersects I-96 and continues north to an intersection with M-59 south of Hartland. The highway turns northeasterly by Runyon Lake and runs toward the city of Fenton. The trunkline passes through town and bends back toward the northwest, running between lakes Ponemah and Fenton. Continuing north, the environment around US 23 transitions to rural farm fields as the freeway approaches the south side of the Flint area.[3][4]

I-75/US 23 northbound approaching the Zilwaukee Bridge near Saginaw

West of Grand Blanc, US 23 meets I-75, and the two freeways merge near the Bishop International Airport and continue along the west side of the Flint metro area.[3][4] I-75/US 23 has an interchange with I-69 near the crossing with the Canadian National Railway line.[7] Continuing northwards through suburban residential areas, the highway crosses the Flint River while running along the west side of the city. In Mount Morris Township, the freeway intersects the northern end of I-475 before meeting M-57 near Clio.[3][4] The highest traffic totals along US 23 in the state of Michigan were recorded by MDOT near the M-57 interchange; in 2009 an average 68,800 vehicles used that section of freeway daily.[9] These traffic counts are expressed in terms of annual average daily traffic (AADT), which is a statistical calculation of the average daily number of vehicles on a segment of roadway.

Near Birch Run, the highway turns northwesterly next to a large outlet mall. Between here and the Saginaw area, the freeway runs through more wooded lands, crossing the Cass River near Bridgeport. I-75/US 23 enters the Tri-Cities (named for Saginaw, Bay City and Midland) when it bypasses Saginaw to the east. The freeway intersects M-46 in Buena Vista Township south of the junction with I-675. North of downtown Saginaw, the freeway crosses the Saginaw River on the Zilwaukee Bridge,[3][4] a "post-tensioned, segmental, [concrete] box girder bridge"[10] that is "infamous" for a series of "construction mishaps, cost overruns, and government foibles."[11]

Northern end of the freeway near Standish

Past the bridge, I-75/US 23 meets the northern end of I-675 and continues through fields and woods to the Bay City area. At exit 162, the freeway meets the eastern terminus of US 10 and the western terminus of M-25 west of downtown. The next interchange north is with the Connector M-13 (CONN M-13) freeway, which was the previous northern end of US 23's freeway in Michigan. The connector runs due northward, and I-75/US 23 turns northwesterly to bypass around Kawkawlin. The highway veers north, crosses the Kawkawlin River and the Pinconning Creek before coming to an interchange southwest of Standish. There, US 23 curves east, separating from I-75. US 23 continues for about three miles (4.8 km) as a freeway which ends at the intersection with M-13 south of Standish.[3][4] The lowest AADT along any freeway section of US 23 in Michigan is the section immediately east of I-75; here the traffic levels drop from 20,763 to 4,466 vehicles per day after US 23 separates from I-75.[9]

US 23 runs north from the end of its freeway along Huron Road through the community of Standish. The trunkline turns northeasterly through lakeshore woodlands after the intersection with Old M-76.[3][4] Northeast of this intersection, the highest, non-freeway AADT level on US 23 was recorded by MDOT at 16,757 vehicles daily.[9] Running through Omer, the highway crosses the Rifle River[3][4] and a line of the Lake State Railway.[7] In between the two crossings, it curves due east on its way out of town. At Hale Road, US 23 meets the southern end of M-65 before it continues east to Au Gres, where it runs along the Saginaw Bay and crosses the Au Gres River. Huron Road meanders northward along the lakeshore, staying inland near Point Lookout. US 23 runs through woods as it follows the Saginaw Bays shoreline northeasterly through Alabaster to Tawas City. The highway intersects the eastern terminus of M-55, runs north and east around Tawas Bay to East Tawas and follows the Lake Huron shoreline to Oscoda.[3][4] Through this area, US 23 runs parallel to the Lake State Railway and crosses into the Huron National Forest.[7][12]

Welcome sign at Omer

Oscoda is the location of the eastern termini of both the River Road National Scenic Byway and County Road F-41. In between those two junctions, the highway crosses the Au Sable River near its mouth, and the trunkline passes by the former Wurtsmith Air Force Base. Huron Road continues north, running next to Van Etten Lake as it leaves the national forest. Further north, it runs along Cedar Lake when it crosses into Alcona County.[4][12] The highway meets the eastern termini of F-30 and M-72 in Greenbush and Harrisville respectively. It also passes Harrisville State Park in the latter community. The highway shifts a bit further inland north of Harrisville, continuing to parallel the railroad through the Mackinaw State Forest. Near Ossineke, the trunkline turns back toward the lake, running along the shoreline of Thunder Bay.[3][4]

When US 23 enters Alpena, it follows State Street through town and turns northwesterly on Chisholm Street. The intersection of Chisholm and Washington streets marks the eastern terminus of M-32. Chisholm Street runs along the Thunder Bay River and crosses the river near Lake Besser. The highway leaves town and runs through rural woodlands to the south shore of Long Lake, curving around the eastern side of the lake. Near the northern end of the lake, US 23 crosses into Presque Isle County and runs along the west shore of Grand Lake. At the north end of that lake, the highway turns west along the Lake Huron shoreline near Thompson's Harbor State Park. The trunkline continues to Rogers City where it bypasses town to the south and west, intersecting F-21 and M-68 in the process; Bus. US 23 runs through downtown. On the other side of Rogers City, US 23 runs along the lake past Hoeft State Park and along Hammond Bay before crossing into Cheboygan County.[3][4] This area had the lowest AADT levels in 2009 at 1,097 vehicles per day.[9]

Sign where US 23 crosses the 45th parallel north

US 23 follows the Lake Huron shoreline through Cheboygan County through woodlands past Cheboygan State Park and Duncan Bay. On the eastern edge of Cheboygan the highway intersects F-05 before following State Street through a commercial district. State Street crosses the Cheboygan River on the Cheboygan Bascule Bridge near the mouth of the river and the dock for the USCGC Mackinaw. On the west side of the river, US 23 meets the northern terminus of M-27 at the intersection with Main Street. State Street continues westerly as C-66 as US 23 turns north on Main Street for a block before resuming west on Mackinaw Avenue. The highway continues along the lake toward Mackinaw City. As it approaches the village, it passes Historic Mill Creek State Park and several motels. At Nicolet Street in town, the highway crosses into Emmet County for the short distance to the highway's national northern terminus at I-75's exit 338.[3][4]

Highway markers for the Dixie Highway (left) and Theodore Roosevelt International Highway (right), both of which predate the modern highway

Before Michigan became a state, the first land transportation corridors were the Indian trails.[13] The original Shore Trail ran roughly parallel to the route of the modern US 23 from the Bay City area to Cheboygan. Another section of the current highway followed the Saginaw Trail between Flint and Saginaw.[14]

Later, during the auto trail era, the modern US 23 also coincided with the east branch of the Dixie Highway and part of the Lower Peninsula section of the Theodore Roosevelt International Highway. The Dixie Highway was created by William S. Gilbreath after he developed the Lincoln Highway. The highway was designed to link the Great Lakes with the Gulf of Mexico, and to commemorate a half century of peace between the North and the South after the American Civil War. At the urging of Governor Woodbridge N. Ferris, the northern terminus was located at the Straits of Mackinac. The highway had two branches in the Lower Peninsula; the eastern branch followed what later became US 23 north of Standish.[15] The Theodore Roosevelt International Highway was named for former US president Theodore Roosevelt after his death in 1919. Overall, this highway ran from Portland, Oregon, to Portland, Maine, by way of Michigan and the Canadian province of Ontario. In Michigan, it also followed US 23 north of Standish.[16]

The highway was also part of the East Michigan Pike, designed to be a counterpart of the West Michigan Pike on the other side of the Lower Peninsula. The original route of the East Michigan Pike included a section along the coast of The Thumb between Bay City and Port Huron and used the same route as the Dixie Highway north of Bay City. Backers of this auto trail lost out in terms of name recognition to the Dixie Highway, relegating the East Michigan Pike to the list of failed auto trails.[17] The southern part of what is now US 23 in the state was also part of the auto trail craze. The Top of Michigan Trail was designated in 1917 from the state line north to the Bay City area, before turning inland along other roadways. The name faded from shortly after the time the Michigan State Highway Department (MSHD)[lower-alpha 1] assigned the first highway numbers in the state.[20]

The first state highways along the US 23 corridor were numbered M-65 from the Ohio line north to the Flint area and M-10 from Flint north to Mackinaw City by July 1, 1919.[21][lower-alpha 2] When originally designated, M-65 was in two sections: the southern segment ran from the Ohio state line north to the Dundee area; the northern section ran between Ann Arbor and Flint by way of Brighton and Fenton.[21] The gap between the two segments was eliminated by the middle of 1926.[23]

US 23 was commissioned on November 11, 1926, with the debut of the United States Numbered Highway System.[2][24] The MSHD removed the M-10 and M-65 designations from the highway at the time. As it was originally designated, US 23 crossed into Michigan from Ohio south of Temperance and ran north to Ypsilanti via Ida and Maybee. Once the highway entered Ann Arbor, it followed the roads that preceded the modern freeway up to Flint. From Flint to Saginaw, US 23 ran concurrently with US 10. On the way north to Bay City, the highway ran on the west side of the Saginaw River before turning north to the Standish area. From Standish to Mackinaw City, US 23 initially took a more inland route through the northeastern Lower Peninsula.[25]

Original 1920s routing of US 23 between Cheboygan and Alpena highlighted in red

Starting in 1929, MSHD started updating the route that US 23 followed through the Lower Peninsula. Late that year, the routing was moved to the east side of the Saginaw River, and M-47 was extended along the former course on the west side of the river.[26][27] During 1930, a set of changes realigned the highway's route through the southeast corner of the state. Near Ida, US 23 was rerouted along M-50 to Dundee and north through Milan to Ann Arbor, bypassing Maybee and Whittaker.[28] US 23 was moved from its inland routing between Omer and Tawas City via Whittemore to follow a shoreline alignment by way of Au Gres along Saginaw Bay around 1932; the former route through Twining and Whittemore became an extension of M-65 and the section from Whittemore east to Tawas City was added to M-55 as a part of these changes.[29][30]

In 1932, US 23 was moved closer to the lakeshore between Spruce and Alpena; the former routing was redesignated M-171.[30] The highway was also moved to a route closer to the lakeshore between Tawas City and Oscoda, with part of the old inland route taking the designation Old US 23.[31][32] A few years later in 1936, US 23 replaced M-72 between Oscoda and Harrisville and followed a new roadway north to the Spruce area. The M-171 designation was removed from its original routing and applied to the 1932 routing of US 23 by way of Mikado and Lincoln.[33][34] In the middle of 1937, US 27 was extended concurrently along US 23 between Cheboygan and Mackinaw City.[35][36] Around the end of the decade, US 23's routing was moved in another location to follow the lakeshore; this time the highway was rerouted between Alpena and Rogers City. M-65 was extended northwards from Lachine through Posen to terminate over the former US 23 routing.[37][38]

US 23 was moved to its current lakeshore routing between Rogers City and Cheboygan in 1940, and M-33 was extended westerly from Onaway to Afton and north to Cheboygan over the former US 23 roadway while M-68 was extended eastward through Onaway to Rogers City.[39][40] In early 1941, a bridge across the Saginaw River connecting Salzburg and Lafayette avenues in Bay City was added to the route of US 23 in the city; at the same time the former routing was redesignated Bus. US 23.[41][42] The highway was also realigned between Hartland and Fenton in 1941.[43][44] By 1945, the northernmost segment of M-65 in downtown Rogers City was redesignated Bus. US 23, and M-65 was truncated to its junction with US 23 southeast of town, removing the concurrency that existed since 1940.[45] North of Dundee, a more direct alignment to Azalia was added to US 23, turning the former routing back to local control in late 1947 or early 1948; at the same time, the last gravel section of the highway was paved near Hammond Bay in northwestern Presque Isle County.[46][47]

Rest area and welcome center near Samaria in Monroe County

One of the first pieces of what would later become part of US 23's freeway route was completed in late 1951 or early 1952, when a two-lane bypass was built around the eastern side of Milan.[48][49] Two years later, a similar bypass was built from Bridgeport to M-81 on the east side of Saginaw, with the old route becoming a Bus. US 23 designation.[50][51] Both bypasses would later be upgraded to four-lane freeways by 1961, with the Saginaw one later incorporated into the route of I-75.[52] When the Mackinac Bridge opened on November 1, 1957, US 23, US 27 and US 31 were extended along the access roadways to the foot of the bridge.[53]

The first future freeway portion of US 23 was built in 1957 from north of Ann Arbor to Whitmore Lake as a divided highway.[54][55] On June 30, 1958, the first stretch of the "Fenton–Clio Expressway" opened, stretching from Fenton to Birch Run.[56] The freeway connection from Dundee south to Ohio was opened on October 1, 1959.[57] In late 1959, the portion from Flint to Birch Run also gained the I-75 designation.[58]

In late 1960 or early 1961, a new I-75/US 10/US 23 freeway was built from the north end of the Saginaw bypass to Kawkawlin, utilizing the Zilwaukee drawbridge (later replaced by the Zilwaukee Bridge) over the Saginaw River; when it opened, MSHD extended M-13 along the former route of US 23 from the northside of Saginaw into Bay City to the end of the freeway at Kawkawlin. Another section connected the Whitmore Lake area with Brighton in the same timeframe.[52][59] General Motors was bidding in 1961 to construct an electronic highway. US 23 between Ann Arbor and Toledo was under consideration to be the location of this project;[60] the testing for such a roadway was ultimately done at Ohio State University instead.[61] By the end of the year, freeway sections opened to bypass Saginaw south and ran south to Birch Run, another connected south from Fenton to Hartland, and a third connected Milan with Dundee.[62] The remaining gaps were eliminated with additional freeway openings in 1962: Brighton to Hartland opened in September,[63] and Milan to Ann Arbor opened in November.[64] The I-75/US 23 freeway north of the Kawkawlin area to Standish opened in 1967, and M-13 was shown on maps following US 23's former route through Linwood and Pinconning after the change.[65][66]

Northern terminus in Mackinaw City

The MSHD requested additional Interstate Highway mileage in 1968 under the Federal-Aid Highway Act of 1968 including a freeway along US 23 between Standish and Mackinaw City.[67] This extension was rejected by Congress on December 13, 1968; instead, Michigan was allotted additional mileage for an extension of I-69 to Flint.[68] Once the last piece of I-75 was completed along the M-76 corridor in November 1973,[69] the I-75 designation was extended north of Bay City on US 23.[70]

The MSHD first proposed a realignment of US 223 in 1965; this change would reroute that highway to replace M-151 in southern Monroe County, and use the US 23 freeway to connect to Sylvania, Ohio.[71] The rerouting change was made in 1977 when Michigan shifted its segment of US 223 as proposed twelve years prior. Instead of running south through Ottawa Lake, US 223 continued east to the US 23 freeway and south into Ohio.[72][73]

The original bridge across the Saginaw River at Zilwaukee was built in 1960 as a bascule bridge to allow shipping traffic to use the river. Opening the drawbridge would back traffic up on I-75/US 10/US 23 for upwards of four hours on holiday weekends.[74] Approved in 1974, construction on the replacement bridge started in October 1979. A major construction accident in August 1982 delayed completion of the new Zilwaukee Bridge; a bridge pier partially collapsed when contractors overloaded a section under construction. The affected 300-foot (91 m) deck segment tilted to rest three feet (0.91 m) higher on one end and five feet (1.5 m) lower on the other.[10] The structure was originally supposed to cost $76.8 million with a 1983 completion date; in the end it cost $131.3 million (equivalent to $263 million in 2021[75]) when the southbound span finally opened on September 19, 1988.[76] The structure is the largest segmental concrete bridge in the country.[77]

While that construction was being done, MDOT truncated US 10 at Bay City in 1986; this removed the concurrency between US 10 and US 23 that existed since 1926.[78][79] A few years later in 1992, the freeway concept for the northeastern LP was revived again when MDOT initiated plans to study and build a new US 23 freeway from Standish northerly to Tawas City, Oscoda or Alpena. This proposal was brought up due to a high level of tourist traffic along the current routing since the mid-1960s.[80] The FHWA mandated additional environmental studies for the project in 2000, and MDOT withdrew the proposals two years later.[81]

External video
US-23 Ann Arbor, Michigan - Flex Lanes at YouTube

In November 2016, construction work on a $92 million project began on the freeway between Ann Arbor and Whitmore Lake. This construction includes replacement of bridges and reconstruction of off ramps.[82][83] A year later, the flex route system opened, using intelligent traffic management and electronic signs to monitor and redirect traffic. The system can open a temporary travel lane on the inner shoulder during rush hour.[8] The flex route project was nationally recognized by American Association of State Highway and Transportation Officials (AASHTO) in 2018 for Operations Excellence.[84] A $150 million extension to the interchange with I-96 is scheduled to begin in 2023 and be completed the following year.[83]

In March 2022, construction work began at the northern end of the freeway portion of US 23 just south of the city of Standish. This will remove a bridge and on-ramp at the end of the freeway, replacing it with a roundabout.[85]